This application relates to a unique hub cap used in wheel end assembly for a tire inflation system. The hub cap includes an internal filtering system for removing contaminants from the air supply before entering the tires.
Tire inflation systems automatically supply air to tires when certain predetermined conditions are met. In a typical situation, the tire inflation system will automatically add air to a tire that becomes under-inflated during vehicle operation. Tire inflation systems include sensors and pressure regulators for monitoring the pressure in each of the vehicle""s tires. When pressure in any tire drops below a predetermined level, the system automatically supplies air to that tire until a desired pressure is achieved.
Some systems include check valves for permitting one way air flow, i.e., air flow from the air supply to the tire, so that unwanted tire deflation does not occur. Other systems include valves for permitting two way air flow, i.e. air flow into and out of the tires, so that variable tire pressures can be achieved depending upon the type of terrain over which the vehicle will travel. For example, on hard surfaces such as packed dirt or concrete a higher tire pressure is preferred whereas on surfaces such as sand or mud a lower tire pressure is preferred for increased traction. Usually the tire inflation systems also include an unloader valve that prevents air from being supplied to a tire if there is a blowout.
The tire inflation systems include an air tank that is mounted on the vehicle. Air is supplied from the tank to the tires by using various methods. All inflation systems must include a rotary connection that allows air to be supplied to the tires during rotation. Some systems include a rotary valve mounted on one end of the axle. In theses systems, air is supplied from the tank to the interior of the axle. Air from inside the axle passes through the rotary valve and is conducted to the tires. Another system supplies air via a hub that is rotatable supported on the axle. Rotary seals are used to provide a sealed environment for air conduction.
When vehicles operate off-road under severe conditions, the air supply can become easily contaminated with dirt particles and other debris, which can clog air supply system components. Air filtering systems are required to remove any contaminants from the air before entering the tires. Current air filters are located with the axle housing. This location is undesirable because it is difficult to replace and/or remove the filters.
Thus, it is desirable to have a wheel end assembly for a tire inflation system that provides a simplified air filtering system that can be easily installed and which utilizes an air filter that is easily accessible for removal, replacement, or cleaning.
A wheel end assembly for a vehicle tire inflation system includes a wheel hub that is rotatably supported on an axle member and a hub cap mounted for rotation with the wheel hub. The axle includes an air supply conduit for conducting an air supply to a passageway formed within the hub cap. The passageway has an inlet in communication with the air supply conduit and an outlet in communication with at least one pneumatic tire. A filter is mounted within the passageway between the inlet and the outlet to remove debris from the air supply. The purified air is supplied to the tire via a tire inlet.
In the preferred embodiment, the hub cap has an inner wall, an outer wall and a flange positioned between the inner and outer walls. The filter is mounted within the hub cap between the inner wall and the flange. The flange preferably has a smaller diameter than the outer wall to create a peripheral gap about the inner circumference of the hub cap. The peripheral gap forms a portion of the passageway between the inlet and the outlet.
In a further preferred embodiment, the hub cap includes a circumferential lip that is in abutting contact with an outer face of the wheel hub at a first axial location. The hub cap defines an inner space between an end of the axle member and the hub cap at a second axial location. Finally, the air supply conduit extends into a seal in the end of the axle member at a third axial location where the third axial location is intermediate the first and second axial locations. The filter is mounted within the inner space at the second axial location such that the hub cap provides air purification at a location axially outward from the wheel hub.
By providing a hub cap with an internal air filter for removing debris from the air supply before entering the tires, the subject invention presents a simplified filtering system that is easy to install. Moreover, the use of an air filter within the hub cap provides easy access for removal, repair, and cleaning.